1. Field of the Invention
This invention relates, in general, to a sheet-stack binding apparatus for the binding of loose sheets to form brochures or books, and in particular to a method and apparatus for feeding strips coated with a fusion adhesive on one of their surfaces to an advancing transport unit.
2. Background Art
Sheet-stack binding apparatus for the binding of loose sheets to form brochures or books using strips coated with a fusion adhesive are described, for example, in DE-PS 2 144 101 as well as in the European Patents EP 0 186 080 and EP 0 412 742. A sheet stack held between clamping elements is pressed in the usual manner onto a fusion-adhesive coated strip which is arranged directly on or above a heated platen. As shown in EP 0 186 080, an adhesive element cut to be adapted to the sheet format can also be pressed by means of a pressure device against the spine of the sheet stack from below and then heated. Using heated lateral pressure elements, the adhesive strip is then folded and pressed against the cover sheets. As described in EP 0 412 742, an abutment can be provided to limit the contact pressure of a sheet stack pressed onto a heated platen so that the sheets are prevented from spreading during the adhesive binding. U.S. Pat. No. 4,797,048 also discloses an apparatus for binding loose sheets by means of fusion-adhesive coated strips, in which a heated platen is resiliently pressed against the strip with a predetermined pressure force in order to obtain an optimum adhesive bond. These known devices are disadvantageous in that only fusion-adhesive strips of one width can be handled unless the devices are converted for that purpose.
Other devices disclosed in the prior art include the Thermomatic-Binder 390 as illustrated in a brochure of the PLANAX Company (1992), which is capable of handling fusion-adhesive coated strips of different widths. However, the strip supply roll has to be exchanged for this purpose and the device has to be adjusted to each different thickness of the sheet stacks to be bound as well as to the different strip widths.